Sulfur and phosphorus bearing lubricant

ABSTRACT

1. IN A LUBRICANT COMPOSITION INCLUDING A BASE OIL OF MINERAL OR SYNTHETIC ORGIN AND A LUBRICATION-IMPROVING ADDITIVE CONTAINING CHEMICALLY BOUND PHOSPHORUS AND SLFUR WHILE FREE FROM CHEMICALLY BOUND HEAVY METAL, SAID ADDITIVE BEING A MEMBER OF THE GROUP CONSISTING OF SULFIDES AND POLYSULFIDES OF PHOSPHORUS, THIOPHOSPHATES, AND PRODUCTS OF THE SULFURIZATION AND PHOSPHORIZATION OF ORGANIC COMPOUNDSS CONTAINING AT LEAST ONE OLEFINIC DOUBLE BOND THE IMPROVEMENT WHICH COMPRISES: (A) A METAL-ORGANIC DITHIOCARBAMATE IN AN AMOUNT SUFFICIENT TO ENCHANCE THE LUBRICATION-IMPROVING EFFECT OF SAID ADDITIVE, (B) SAID DITHIOCARBAMATE HAVING THE FORMULA   (R1-N(-R2)-C(=S)-S-)Z ME   WHEREIN R1 AND R2 ARE MEMBERS OF THE GROUP CONSISTING OF STRAIGHT-CHANED ALKYL, BRANCHED ALKYL, AND CYCLOALKYL, SAID MEMBERS HAVING 2 TO 10 CARBON AOMS, ME IS A METAL OF THE GROUP CONSISTING OF ZINC LEAD, TIN, TUNGSTEN, MOLYBDENUM, NIOBIUM, LANTHANUM, ANTIMONY, BISMUTH, CHROMIUM, VANADIUM, AND CADMIUM, AND Z IS THE VALENCE OF SAID METAL AND 2 OR 3 (C) THE COMBINED AMOUNT OF SAID LUBRICATION-IMPROVING ADDITIVE AND OF SAID DITHIOCARBAMATE BEING BETWEEN 0.1% AND 20% OF THE WEIGHT OF SAID BASE OIL.

United States Patent 3,840,463 SULFUR AND PHOSPHORUS BEARING LUBRICANT Rasmus Froeschmann, Irschenhausen, and Friedrich Spriigel, Munich, Germany, assignors to Optimol- Olwerke GmbH, Munich, Germany No Drawing. Filed Feb. 17, 1972, Ser. No. 227,234 Claims priority, application Germany, Feb. 24, 1971, P 21 08 780.9 Int. Cl. C10m N48 US. Cl. 252-42.7 7 Claims ABSTRACT OF THE DISCLOSURE The performance of lubricants having a mineral oil or synthetic oil base can be improved greatly by N-dialkyldithiocarbamates of zinc, lead, tin, tungsten, molybdenum, niobium, lanthanum, antimony, bismuth, chromium, vanadium, or cadmium or of dithiophosphates of these heavy metals esterified with alkyl, aryl, or alkyl-aryl groups in synergistic cooperation with additives free from heavy metals, but containing sulfur and phosphorus, such as sulfides of phosphorus and known addition agents.

This invention relates to heavy-duty lubricants, and particularly to addition agents for such lubricants and to the lubricants containing the same.

It is known to mix lubricant base oils, which may be petroleum fractions or synthetic liquids, with compounds containing sulfur and phosphous to improve the lubrication performance.

It has now been found that such base oils can be improved to an extent not available heretofore by the addition of a synergistic mixture of metal-organic compounds and compounds free from heavy metal and containing sulfur and phosphorus. The mixtures of the invention are added to natural or synthetic base oils in amounts of 0.1% to 20% of the weight of the base, the lower limit being useful for lubricants intended for relatively light duty, and the higher limit typically being reached in concentrates intended to be diluted with more base oil. For heavy duty service in automotive engines and transmissions the lubricant ready for use should contain between 1 and 12% of a mixture of the invention.

The metal-organic component in the mixtures of the invention contains zinc, lead, tin, tungsten, molybdenum, niobium, lanthanum, antimony, bismuth, chromium, vanadium, or cadmium. The organic moiety of the compound should include alkyl radicals, also sulfur and/or phosphorus. The metal-organic compounds best suited for the mixtures of the invention are N-alkyldithiocarbamates and alkyl, aryl, and alkyl-aryl dithiophosphates of the heavy metals enumerated.

The metal-organic compounds of the invention thus have the formula (S=AS ,-Me S,gO wherein A is In these formulas R R are members of the groups consisting of straight-chained, branched, and cyclic alkyl having 2 to 10 carbon atoms, and R R may be members of the same group or phenyl, o-alkylphenyl, or p-alkylphenyl, the alkyl groups of the alkylphenyls having 1-6 carbon atoms.

Me is one of the heavy metals referred to above, y is 0 or an integer up to 4, x is zero or an integer up to 6, zis2or3,andwis1or2.

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z is preferably 2 when Me is molybdenum, cadmium, zinc, lead, tin, tungsten, chromium, niobium or lanthanum. z is preferably 3 when Me is antimony or bismuth.

w is preferably 1 when Me is antimony, bismuth, cadmium, zinc, lead, tin, niobium or lanthanum, and is 2 when Me is tungsten, chromium, vanadium or molybdenum.

x and y are preferably 0 when Me is tin, lead, zinc, niobium, lanthanum, cadmium, antimony or bismuth. x is preferably 2, 4 or 6, and y is 2, 4 or preferably 0 when Me is molybdenum, tungsten, vanadium or chromium.

The dithiocarbamates and dithiophosphates of heavy metals according to the above formulas are known, and many are staple articles of commerce sold, for example, by R. T. Vanderbilt Co. Inc. of New York, NY. the following compounds are representative of the metal-organic compounds in the mixtures of the invention:

Lead-N-diethyldithiocarbamate,

Lead N-diamyldithiocarbamate, Lead N-dihexyldithiocarbamate, Lead N-dicyclohexyldithiocarbamate, Lead N-diheptyldithiocarbamate, Lead N-dioctyldithiocarbamate, Lead N-dinonyldithiocarbamate, Lead N-didecyldithiocarbamate, Lead N-di-n-buty1dithiocarbamate, Lead N-diisobutyldithiocarbamate, Lead N-dicyclopentyldithiocarbamate,

and the corresponding N-dialkyldithiocarbamates of zinc, cadmium, tin, lanthanum, and niobium in which 1 is 2, w is 1, and x and y are zero; the corresponding N-dialkyldithiocarbamates of bismuth, antimony, and lanthanum, in which z is 3, w is 1, and x and y are 0; the corresponding N-dialkyldithiocarbamates of tungsten, molybdenum, vanadium, niobium, and chromium wherein z is 2, w is 2, y is 2 or 4, and x is 2 or 4, also Antimony, 0,0-diethyldithiophosphate, Antimony 0,0-dipropyldithiophosphate, Antimony 0,0-dibutyldithiophosphate, Antimony 0,0-dipentyldithiophosphate, Antimony 0,0-dicyclopentyldithiophosphate, Antimony 0,0-dihexyldithiophosphate, Antimony O,O-dicyclohexyldithiophosphate, Antimony 0,0-diheptyldithiophosphate, Antimony 0,0-dioctyldithiophosphate,

Antimony 0,0-dinonyldithiophosphate, Antimony 0,0-didecyldithiophosphate, Antimony 0,0-diphenyldithiophosphate, Antimony 0,0-di-o-methylphenyldithiophosphate, Antimony 0,0-di-p-methylphenyldithiophosphate, Antimony 0,0-di-o-ethylphenyldithiophosphate, Antimony 0,0-di-o-propylphenyldithiophosphate, Antimony 0,0-di-o-butylphenyldithiophosphate, Antimony 0,0-di-o-pentylphenyldithiophosphate, Antimony 0,0-di-o-hexylphenyldithiophosphate, Antimony 0,0-di-p-hexylphenyldithiophosphate,

the corresponding bismuth and lanthanum N-dialkyldithiophosphates in which z is 3, w is one, and x and y are 0; the corresponding 0,0-disubstituted dithiophosphates of lead, zinc, tin, and cadmium wherein z is 2, w is 1, and x and y are 0; the corresponding 0,0-substituted dithiophosphates of molybdenum, tungsten, chromium, vanadium, and niobium wherein z is 2, w is 2, x is 2, and y is 2.

The metal-organic compounds are preferably present in lubricants of the invention which are ready for use in amounts of 0.5% to 4%, and may be present in concentrates in amounts of up to 15%, all percentage figures being by weight unless otherwise stated specifically.

Suitable sulfur-phosphorus compounds free from heavy metal include the phosphorus sulfides, such as P 8 P (P 8 and P 8 and corresponding polysulfides containing additional sulfur, also thiophosphates in which phosphorus is directly bound to sulfur, and the like. Sulfur may be replaced in these compounds partly or entirely by selenium or tellurium. Preferred compounds of this type are obtained by sulfurization and/or phosphorization of organic substances containing one or more olefinic double bonds, e.g. sperm oil butadienes or terpenes. Sulfurized sperm oil esterified with dithiophosphate, sulfurized terpene esterified with dithiophosphate, and sulfurized sperm oil phosphated by reaction with phosphorus pentoxide are among the more complex compounds free from heavy metals which constitute the second component of the synergistic mixtures of this invention.

The last-mentioned compounds also are known and constitute ingredients of complex commercial mixtures, not capable of precise structural analysis, such as Anglamol 99 (Lubrizol Corp., Cleveland, Ohio), which has a nominal sulfur content of 31.5% and a phosphorus content of 1.75%.

The sulfur and phosphorus bearing components of the mixtures of the invention which are free of heavy metal may be present in the improved lubricants in the same amounts as the metal-organic compounds, and the same ranges of concentration are preferred. The individual values, however, are preferably chosen in such a manner that the sulfur-phosphorus compounds are present in amounts of two to six times the weight of the metal-organic compound.

The mixtures are combined with base oils conventional in the manufacture of lubricants. Good results are obtained with mineral oils having viscosities between 1.8 E. (Engler) and C. to 35 E. at 50 C. Synthetic oils, such as diisodecyl phthalate, trimethyl adipate, or the dioctyl ester of sebacic acid, are most favorably affected at viscosities between 1.8 E. at 20 C. to about 65 E. at 50 C.

As compared to known lubricants, the lubricant compositions of the invention substantially reduce wear of the lubricated surfaces, improve the adhesion of the interfacial lubricant film, enhance the oxidation resistance and thus the useful life of the lubricant, and reduce the coefiicient of friction and thus the operating temperature.

It is a particular advantage of this invention that the listed improvements are available over very wide ranges of viscosities as mentioned above. Thus, oils of low viscosity may be employed where lubricants of high viscosity were required heretofore, as in automotive transmissions and differential gearing. The same lubricant composition of the invention may be employed in an automotive vehicle in the transmission and differential gearing as well as in the engine. When the components are suitably matched, the lubricant compositions of the invention may be adapted to a wide variety of operating conditions and unusual applications, and only few preliminary tests are needed for arriving at the most suitable composition.

The following Examples further illustrate the invention. In these Examples, lubricant compositions of the invention and controls were tested in an apparatus commercially available under the name Lubrimeter from Sommer & Runge in Berlin, Germany. The specific testing device employed was of the improved Lohmaier design. Its basic elements are a piston pin and two small, rotating rollers frictionally engaging the pin. The wear of the pin and of the rollers under a constant load is determined. The apparatus also permits the measurement of the coefiicient of friction, temperature, and contact pressure at the end of a test run. The condition of the engaged surfaces, particularly changes in the surface of the rollers, can be measured and/ or observed.

In all tests, the velocity of relative sliding movement was 0.6 m./sec. The relative travel amounted to 51,840

m. in 24 hours. 0.4 liter oil was circulated to make the rate of oil application 45 liters per hour.

EXAMPLE 1 Composition I II III Wear loss, mg 0. 074 1. 49 0. 66 Terminal contact pressure, kp./mm." 91 27 36 Coefiicient of friction, t, after-- 5 minutes 0. 066 0. 078 0. 054

12 hours. 0. 058 0. 094 0. 052

24 hours 0. 054 0. 090 0. 053 Condition of contact are Rough Sludge formation Slight Heavy 1 Very smooth. 1 Smooth.- 3 Very heavy:

As is evident from the above data, replacing 1.5 Anglamol by the molybdenum compound reduces the weight loss by wear to approximately one twentieth although the metal-organic compound, even when used alone in an amount of 8%, only moderately reduces wear. The contact pressure figures, as determined at the end of the test runs, indicate the enlargement of the contact area by wear and confirm the wear values determined by weight loss. The condition of the frictionally engaged surfaces is far superior with the combination of the invention than with either component alone, resulting in a corresponding reduction in sludge. The coeificient of friction produced by the metal-organic compound alone is somewhat lower initially, but there is no significant difference after 24 hours.

EXAMPLE 2 Cnmpn ih'nn IV V Wear loss, mg 0. 115 O. 148 Terminal contact pressure, kp./mm. 76 67 Coefficient of friction, [4, after 5 minutes O. 076 0.095

12 hours 0. 059 0. 070

24 hours 0. 059 0. 067 Condition of contact areas Sludge formation Shght l Very smooth. 1 Fine grooves. 8 Very slight.

EXAMPLE 3 Antimony dioctyldithiophosphate was substituted for the zinc compound of Compositions IV and V in the Compositions VI and VII respectively with the following results:

Cnmpn itinn VI VII Wear loss, mg 0. 074 0. 60

Terminal contact pressure, kp./mm. 102 Coeflicient of friction, after- 12 hours 0. 060 0. 062

Sludge formation 1 Very smooth. 3 Fine grooves.

EXAMPLE 4 The following data were obtained by testing a composition VIII difiering from Composition VI by containing 8 Very heavy.

1.5 lead diamyldithiocarbamate instead of the antimony compound, all other conditions being unchanged.

When 1.5 cadmium di-(Z-ethylhexyl)-dithiophosphate was substituted for the lead compound in Composition VIII, the test results obtained with the resulting Compound IX under otherwise identical conditions were as follows:

Wear loss, mg. 0.173. Terminal contact pressure, kp./mm. 65. Coeflicient of friction, 11.:

After 5 min 0.078.

After 12 hours 0.061.

After 24 hours 0.062. Condition of contact areas Very smooth. Sludge formation Moderate.

EXAMPLE 6 Lead N-diamyldithiocarbamate in an amount of 1.5% was mixed with the base oil of viscosity SAE 90 and 6.5% was mixed with the base oil of viscosity SAE 90 and 6.5% Anglamol 99 as in the preceding Examples to produce a Composition X which was tested under the standard conditions described above. The results were as follows:

Wear loss, mg. 0.050. Terminal contact pressure, kg./mm. 112. Coeflicient of friction, a:

After5 min. 0.068.

After 12 hours 0.049.

After 24 hours 0.048. Condition of the contact areas Very smooth. Sludge formation None.

EXAMPLE 7 A Composition XI was tested as described above. It contained zinc N-diamyldithiocarbamate instead of the lead compound in Composition X.

Wear loss, mg. 0.098. Terminal contact pressure, kp./mm. 80. Coeflicient of friction, 1.:

After 5 minutes 0.070.

After 12 hours 0.053.

After 24 hours 0.053. Condition of the contact area Very smooth. Sludge formation None.

EXAMPLE 8 Composition XII yielded the test results indicated below. It differed from Composition X in containing 1.5 cadmium N-diamyldithiocarbamate instead of the corresponding lead compound.

Wear loss, mg. 0.122. Terminal contact pressure. kp./mm. 73. Coefiicient of friction, ,u:

After 5 minutes 0.075.

After 12 hours 0.064.

After 24 hours 0.063. Condition of contact areas Very smooth.

Sludge formation Very slight.

6 EXAMPLE 9 In the procedure of Example 5, 1% molybdenum di-(2- ethylhexyl)-dithiophosphate and 0.5% zinc di-(Z-ethylhexyl)-dithiophosphate were substituted for the corresponding cadmium compound, and the Composition XIII so obtained yielded the following test results under the standard conditions reported above:

Wear loss, mg. 0.065. Terminal contact pressure, kp./mm. 100. Coeflicient of friction, a:

After 5 minutes 0.060.

After 12 hours 0.051.

After 24 hours 0.050. Condition of the contact area Very smooth. Sludge formation Very slight.

The tests described in the several Examples employed the same base oil and the same sulfur and phosphorus bearing component free from heavy metal and the same weight ratio of the metal-organic compounds to the other components to permit direct comparison of the results obtained. Substantially the same relationship of the test results was found when the mineral oil base of SAE was replaced by a fraction of lower viscosity or by a synthetic lubricating oil. A combination of 1.5% metalorganic compound and 6.5 Anglamol 99 was found to produce particularly good lubricants with the mineral oil base used, but the ratio had to be varied within the limits indicated above to produce the best possible lubricant characteristics for other base oils, mineral or synthetic, and was readily determined for each particular set of conditions by a few elementary trial runs. No specific rules can be based on physical or chemical characteristics of the base oil or of the additives.

Anglamol 99 is merely representative of the phosphorus and sulfur bearing additive compositions, usually of undefinable chemical composition, which are now on the market, and tests performed with other proprietary products and with the well-defined sulfides of phosphorus show the synergistic cooperation with the metal-organic compounds described above.

While the invention has been described with particular reference to specific embodiments, it is to be understood, therefore, that it is not limited thereto, but is to be construed broadly and restricted solely by the scope of the appended claims.

What is claimed is:

1. In a lubricant composition including a base oil of mineral or synthetic origin and a lubrication-improving additive containing chemically bound phosphorus and sulfur while free from chemically bound heavy metal, said additive being a member of the group consisting of sulfides and polysulfides of phosphorus, thiophosphates, and products of the sulfurization and phosphorization of organic compounds containing at least one olefinic double bond, the improvement which comprises:

(a) a metal-organic dithiocarbamate in an amount sufficient to enhance the lubrication-improving effect of said additive,

(b) said dithiocarbamate having the formula wherein R, and R are members of the group consisting of straight-chained alkyl, branched alkyl, and cycloalkyl, said members having 2 to 10 carbon atoms, Me is a metal of the group consisting of zinc, lead, tin, tungsten, molybdenum, niobium, lanthanum, antimony, bismuth, chromium, vanadium, and cadmium, and z is the valance of said metal and 2 or 3,

(c) the combined amount of said lubrication-improving additive and of said dithiocarbamate' being between 0.1% and 20% of the weight of said base oil.

2. In a composition as set forth in claim 1, said metal being lead, zinc, or cadmium. Y

3. In a composition as set forth in claim 1, R and R being equal.

4. In a composition as set forth in claim 1, R and R being amyl.

5. In a composition as set forth in claim 1, the amount of said lubrication-improving additive being between one and six times the weight of said dithiocarbamate.

6. In a composition as set forth in claim 5, said phosphorus being directly bound to said sulfur in said lubrication-improving additive.

7. In a composition as set forth in claim 5, said lubrication-improving additive being a phosphorus sulfide.

. 8 4 References Cited UNITED STATES PATENTS HELEN M. S. SNEED, Primary Examiner U.S. c1.v X.R.

E E E E E 

1. IN A LUBRICANT COMPOSITION INCLUDING A BASE OIL OF MINERAL OR SYNTHETIC ORGIN AND A LUBRICATION-IMPROVING ADDITIVE CONTAINING CHEMICALLY BOUND PHOSPHORUS AND SLFUR WHILE FREE FROM CHEMICALLY BOUND HEAVY METAL, SAID ADDITIVE BEING A MEMBER OF THE GROUP CONSISTING OF SULFIDES AND POLYSULFIDES OF PHOSPHORUS, THIOPHOSPHATES, AND PRODUCTS OF THE SULFURIZATION AND PHOSPHORIZATION OF ORGANIC COMPOUNDSS CONTAINING AT LEAST ONE OLEFINIC DOUBLE BOND THE IMPROVEMENT WHICH COMPRISES: (A) A METAL-ORGANIC DITHIOCARBAMATE IN AN AMOUNT SUFFICIENT TO ENCHANCE THE LUBRICATION-IMPROVING EFFECT OF SAID ADDITIVE, (B) SAID DITHIOCARBAMATE HAVING THE FORMULA 